Bucholz Relay

7/28/2019 Bucholz Relay

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BUCHHOLZ RELAY

FEATURES

AT-101

(Gas & Oil Operated)25mm, 50mm, 80mm

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Castings treated against porosity through a special process.

Unique internal design of 'housing' prevents false air traps on top of the relay.

Well designed internal layout gives clear view of colour of gas inside the relay through glass window for fault analysis.

Bucket type float design with inherent ability to withstand vacuum treatment of transformers.

Built in test facility for checking continuity of both Alarm and Trip circuits.

Anti-vibration custom built mercury switches give high stability against mechanical shocks and vibrations.

ATVUS relays are approved by most of the consultants, Power Projects and Electricity Boards in India.

IN SERVICE TO THE TRANSFORMER INDUSTRY SINCE 1971

GOR-1 (25mm)

GOR-2 (50mm)

GOR-3 (80mm)

SRI



GENERAL WORKING

APPLICATIONS

Power Transformers are considered

to be a highly reliable type ofequipment, yet, in order to ensure the

continuity of service that modern

condit ions demand, protective

devices are required. The purpose of

such devices is to disconnect faulty

apparatus before large-scale damage

is caused by a fault to the apparatus

or to other connected apparatus.

Such devices generally respond to a

change in the current or pressure

arising from the faults and are used

for either signaling or tripping the

circuits.

Protective devices in the ideal case

must be sensitive to all faults, simple

in operation, robust for service and

economically feasible. Considering

liquid immersed transformers, a

near-ideal 'protective device' is

available in the form of Gas and Oil

relay described here. The relay

operates on the well-known fact that

almost every type of electric fault in a

'liquid immersed transformer' gives

rise to gas. This gas is collected in the

body of the relay and is used in some

way or other to cause the alarm or the

tripping circuit to operate.

The principle of the Gas and Oil relay

was first successfully demonstrated

and utilized by 'Buchholz' many yearsback. In a series of experiments

carried out extensively in Germany it

was proved that the Relay is capable

of bringing to light incipient fault

thereby preventing further spreading

of the fault and extensive damage and

thus saving expensive and protracted

repairs. So successful is the principle

of this Relay that despi te the

continued search for better protectivedevices in other electrical fields the

Gas-and-Oil Relay is still on its own in

providing protection against a variety

of faults.

The function of a double element

relay will be describedhere.During normal operation of a

transformer the Buchholz relay is

completely filled with oil. Buoyancy

a n d t h e m o m e n t d u e t o

counterweights keep the floats in

their original top positions.

In the event of some fault in the

interior of the transformer tank, gas

b u bb le s a r e p ro du ce d w h ic h

accumulate in the Buchholz relay on

the way to the conservator. In

consequence, the oil level in the relay

enclosure drops which in turn lowers

the upper bucket.

This causes the mercury switch to

operate an alarmsignal.

The lower bucket does not change its

position, because when the gas

reaches the upper inside wall of thep ip e i t c an e sc ap e i nt o t he

conservator. Hence, minor fault in the

transformer tank will not trigger the

lower switching assembly and will

not trip the transformer.

In case the liquid continues to drop

due to loss of oil, the lower bucket

also goes down. In consequence, the

lower switching system operates if

the level of oil goes below the bottom

level of the pipe connected to the

relay.

Alternately in the event the liquid flow

exceeds a specific value (which is

continuously adjustable, by means of

a flap) the lower bucket is forced

down, thus triggering the lower

switchingsystem to operate.

As the liquid flow rate decreases, or the level of the liquid rises, the bucket

returns to its original position. The

single element relay has only Trip

element and it responds to only oil

surges. The method of operation is

similar to that described for double

element relay. Single element relays

are suitable for potential transformersand onload lapchangers.

The single element oil Surge relay has

been specifically designed for use

with on load tap change equipment

and it will by-passnormal amounts of

gas which are generated by tap

change operations and will only

respondtooilsurgesandlossofoil.

Double element relays can be used in

detecting minor or major faults in a

transformer. The alarm element will

operate, after a specified volume of

gas has collected to give an alarm

indication. Examples of incipient

faults are

(a) Broken-downcore bolt insulation

(b) Shorted laminations

(c) Bad contacts

(d) Overheating of part of windings

The alarm element will also operate in

the event of oil leakage, or i f air gets

intotheoilsystem.

The trip element will be operated by

an oil surge in the event of more

seriousfaults such as

(a) Earth faults

(b) Winding short circuits

(c) Punctureof bushings

(d) Short circuit between phases

The trip element will also be operated

if a rapid loss of oil occurs. Single

element relays can be used to detect

either incipient or major faults in oil

f i l led pot enti a l t ransform ers,reactors, capacitors etc. A special

single element relay is available for

the protection of on load tap-change

equipment.



BASIC CHARACTERISTICS

FUNCTIONAL TEST &ELECTRICAL CONNECTION

INSTALLATION

& MAINTENANCEThe Gas and Oil Relay provides

protection against a number of internal

faults and is also able to indicate inseveral cases the type of fault. This is

possible because the gas collected in

relay can, from its colour, odour and

composition, indicate where the fault

may be and what its nature is. By

examining the gases collected it is

possible to infer thenatureof fault.

Thus :

(a) If the gas is colourless and

odourless or with only a faint

odour of oil, the gas is air trapped

intheoilortheinsulation.

(b) If the gas is Greyish white with

sharp and penetrating odour and

non-inflammable it is due to

overheated or faulty insulation

(fuller boardetc.)

(c) If the gas is Yellowish in colour and

inflammable it maybe due tosurface leakage on material like

wood.

(d) If the gas is dark Grey and

inflammable it may be due to a

flashover in oil or due to excessive

overheating of the oil caused by a

fault in the winding or the core.

On the operation of the alarm if

investigation of the collected gas does

not indicate a serious fault it ispossible to leave the transformer in

service till it is convenient to carry out

a t h or o ug h i n sp ec t io n . T hi s

occurrence is possible on a newly

commissioned transformer due to air

trapped in the oil or the insulation. On

repeated and frequent alarm signals

the transformer should be taken out of

servicefor thorough check up.

A test system is provided in

the Buchholz relay that allows the

functional test of the upper and lower

switching system.

To test therelay function loosen the nuton the Test Key and rotate the key with

a screwdriver in the anticlockwise

direction till the SLOT on the Test Key

points towards the T/L position. Both

the alarm (upper switching system)

and Trip (lower switching system) will

show continuity.

On bringing the SLOT on the Test Key

to S (service) position by rotating the

key clockwise the Alarm and Trip

circuits will not show continuity. The

circuits will be actuated to 'ON'

position only when there will a fault in

the transformer.

Repeat the functional test each time a

relay is started or maintenance

completed.

Screw the test pump to

the test cock.

Open the test cock and pump air gently

into the Buchholz relay until the upper

switching system operates.

For operating the lower switching

system air has to be pumped suddenly

with a jerk which will in turn operate

the lower switching system. The Trip

element may not operate with a cyclepump.

To allow

installation of the 'single wire' open the

terminal box cover comprising of the

name plate and the instruction sticker

on the backside. Then pass the wire

through one of the three conduit

screwings into the terminal box. The

upper two studs are terminals for theAlarm switching circuit and are

denoted by A. Likewise the lower two

studs are terminals for the Trip

switchingcircuit and are denoted by T.

For

installing the relay into pipe-lineproceedsasfollows:

To fill

the Buchholz relay, proceed as

describedbelow :

The Buchholz relays

are not sensitiveto external influences.

No servicing is needed during

operation. On routine inspections of the protection equipment, test the

function of the Buchholz relay as

described earlier and check the alarm

and trip devices connectedto them.

Testing the relay Function with the

Test Key :

Testing the relay function with the

Test Pump :

Electrical Connection :

Installation into pipeline :

Filling with Insulation Liquid :

Maintenance :

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See that the Buchholz relay is

positioned with the arrow pointing

to wa rd s th e co ns er va to r, th e

connection box is the Y Plan

(Vertical) and the Test Cock. (1.7)

and airvent cock(1.8) are atthe top.

Mount the Buchholz relays as close

as possible to the tank in the pipeline

b e t w e e n t r a n sf o r m er a n dconservator.

Keep pipe bends as wide as possible.

Avoid close bends.

Make sure pipe ascends to the

conservator at angle between three

degrees to seven degrees.

See that the relay enclosure is not

subjected to stress. If necessary, use

expansioncompensators.

Ensure that the slot on the Test Keyremains in the T/L (Test/Locking)

position during storage or loose

transportation of the relay.

Ensure that the slot on the Test Key

remains in the 'S' (Service) position

andthe TestKey Bolt is Tightenedjust

before commissioningof the relay.

Remove the protective nut from the air vent cock.

Open the air vent cock to let air escapeuntil insulationliquid emerges.

Shut theair vent cock.

Checkliquid level in conservator.



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Due to our policy of continuous product improvement, dimensions and designs are subject to change.

No. Of Switching Systems

Transformer Rating (MVA)

Main Dimensions (mm)

Flange Dimensions (mm)

Pipe Bore (mm)

Surge Test (TRIP) (cm/s)

Gas Volume (ALARM) (cc)

Velocity Test (cm/s)

Element Test

High Voltage TestInsulation Resistance Test

Porosity Test

Mechanical Strength Test

Current Rating of Switch

Resistance of The Switch

2

below 1

250

128

205

1” Conduit

72

M 10

78 square

25

70 to 130

90 to 165

70 to 130

With oil, at 1.4 Kg/cm for 15 minutes

2000 V at 50 Hz for 1 minuteGreater than 10 megaohms with 500 V meggar

With oil, at 1.5 Kg/cm for 4 hours

2

2

With oil, at 8 Kg/cm for 1 minute

2 Amp at 240 V, 50 Hz AC/DC

Not to exceed 0.1 ohm across the electrodes of mercury switch

2

2

1 to 10

250

184 or 215

205

1”

115

18

150

50

75 to 140

175 to 225

75 to 140

Conduit

2

above 10

270

215

220

1”

145

18

185

80

90 to 160

200 to 300

90 to 160

Conduit

1

OLTC

170

119

200

3/4”

72

M 10

78 square

25

45 to 60

N.A.

45 to 60

Conduit

P.C.D.

Holes / Thread

Flange Dia.

IS 3637, Clause 7.6

IS 3637, Clause 7.5

IS 3637, Clause 7.8

IS 3637, Clause 7.4

IS 3637, Clause 7.3IS 3637, Clause 7.3

IS 3637, Clause 7.2

IS 3637, Clause 7.7

IS 3637, Clause 3.3

IS 3637, Clause 3.3

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RELAY TYPE

RELAY TYPEGOR 1

B

RELAY TYPEGOR 2 & 3

RELAY TYPESRI

GOR 1 GOR 2 GOR 3 SRI

INDUSTRIES689, Block ‘O’, New Alipore, Kolkata - 700 053, INDIA

Phones: (91-33) 24001101, 24009885 Fax: (91-33) 24007443, 24007043 E-mail: [email protected]

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Bucholz Relay

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